1. Field of the Invention
The present invention relates to a roaming service method and system of wireless private network systems. More particularly, the present invention relates to a method and system for carrying out a roaming service to wireless private network systems in a multi-zone, by which a subscriber registered in a first wireless private network system can be provided with a call service from a second wireless private network system when moved to a service area of the second wireless private network system.
Herein the term “multi-zone wireless private network system” indicates a network system constituted of same type of wireless private network systems having their own service areas different from one another, in which when a subscriber registered in a first wireless private network system moves out of a service area of the first wireless private network system to visit or roam a service area of a second wireless private network system, the second wireless private network system can provide a call roaming service to the roaming subscriber through cooperation with the first wireless private network system. That is, the respective wireless private network systems located in respective regions of the multi-zone can cooperate with one another, so that the subscriber can be provided with a variety of services from any regional wireless private network system when visiting or roaming the same.
2. Description of the Related Art
In general, wireless private network systems provide services to subscriber terminals registered in their own service areas. When a subscriber terminal registered in a first wireless private network system visits or roams a service area of a second wireless private network system, the subscriber terminal cannot be provided with any service from the wireless private network systems. That is, the subscriber terminal or mobile terminal can be provided with a communication service such as call origination, call receiving and other additional functions only from the first wireless private network system.
In a conventional business communication system of wireless private network systems (e.g., PABX), when a wireless terminal registered in a first wireless private network system moves to a service area of a second wireless private network system, a user manually sets a specific function such as call forwarding or requests such a specific function from a system manager in order to be provided with a roaming service. At present, wireless terminals are increasingly used in a business communication network (e.g., business in-plant wireless network system) since they can be used for communication without restraint in place or time. Such tendency requires an automatic roaming function together with various additional services (e.g., SMS: Short Message Service) based upon the automatic roaming function.
Incorporated by reference herein are U.S. Pat. No. 6,697,621 to Mehmet Taha et al. entitled METHOD AND APPARATUS FOR PROVIDING SERVICES IN A PRIVATE WIRELESS NETWORK which discusses use of a visitor location register (VLR) of a private wireless network that is operable to interrogate multiple home location registers (HLRs) due to detection of a roaming subscriber. The VLR may download one or more subscriber profiles from the multiple HLRs in order to support a variety of services to be offered to the subscriber within the private wireless network. The private wireless network may be embedded within the public wireless network, and the VLR may communicate with both a private network HLR and a public network HLR; U.S. Pat. No. 6,721,306 to Robert D. Farris, et al. entitled PUBLIC WIRELESS/CORDLESS INTERNET GATEWAY which discusses an automatic verification mode, wherein the system communicates with a home location register (HLR) associated with a handset to verify authorization. a wireless gateway system also obtains customer profile information from the HLR and stores that data in a visitor location register (VLR) assigned to the handset. In the preferred embodiment, a central database, accessible via the public packet switched data network, maintains the HLR records; and U.S. Pat. No. 6,016,425 to Cecil H. Bannister entitled HYBRID MULTIZONE CALL DELIVERY SYSTEM which discusses conventional systems, wherein when a roaming portable enters a zone, the portable initiates a registration process. In this registration process the ID and location of the portable device is communicated to a central node to update a Home Location Register (HLR) in a central node. The central node uses the information in its home location register to deliver an incoming call to the portable at the zone where that portable is registered. Bannister's hybrid multizone call delivery system delivers calls to portables by broadcasting from a central node a portable identification number (PIN) and dial-in number (DN) to all the zones in the system. Portables register their presence in zones as they roam throughout the coverage area. When a zone matches a broadcast PIN to a PIN registered therein, a zone controller pages the portable and initiates a call back to the broadcast DN. Upon receipt of the call back, the central node connects the incoming call to the portable through the call back connection. Bannister then teaches it is only necessary to maintain local visitor location register (VLRs) at each zone, and it is not necessary to maintain a home location register (HLR), as is required in conventional systems; and U.S. Pat. No. 6,747,961 to Walid Ahmed et al. entitled MOBILITY MANAGEMENT FOR A MULTIMEDIA MOBILE NETWORK discusses mobility management issues within a packet-based multiaccess mobile communications system, which includes a plurality of mobile user stations and a plurality of network nodes, are provided. Location management techniques include tracking and/or locating mobile stations within the system. The system makes use of home and visiting location registers in which information such as mobile station addresses and/or host names associated with mobile stations are stored.